1. Field of the Invention
This invention relates to power supply systems and, more particularly, to control arrangements for an inverter adapted to supply power in an uninterruptible system; that is to say, a system in which the load is critical and requires a continuous source of power. If the main power supply should fail, the load, for example, a computer or the like, would not lose its memory contents since an emergence power supply is always available. Moreover, in such system it is required that transfer to the emergency power supply (namely, battery) be instantaneous, and that the emergency supply be extremely well regulated.
Accordingly, it is extremely important to be able to control the inverter in such a critically vital system and to protect it against all kinds of malfunctions and hazards to which it may become exposed.
2. Background Art
In order to provide background material for an understanding of one context in which the present invention may be incorporated, reference may be made to U.S. Pat. No. 3,999,077. In such patent, an uninterruptible power supply system is disclosed and the general layout for the system is depicted. The system of that patent provides a fault detection means, which actuates a transfer switch if the main power fails, so as to cause the batteries, which are continuously charged from a rectifier, to supply power to the load; alternately, if the inverter should develop a fault, the fault detection means will cause the inverter to be disconnected from the system.
In contrast to the system of U.S. Pat. No. 3,999,077, the present invention provides that the power is instantly available to the load. Since a transfer switch is not required, the delay due to such transfer switch is avoided. This is referred to as an on-line system.
A typical inverter circuit that may be used in an uninterruptible or similar power supply system can be appreciated by reference to U.S. Pat. No. 3,376,493. In that patent a control oscillator is disclosed, such oscillator furnishing square wave signals to an inverter circuit which includes SCR devices.